Bridge apparatuses are available to connect multiple terminal apparatuses. Each bridge apparatus has multiple physical ports coupled to the terminal apparatuses, for example, personal computers, routers, and so on. The bridge apparatus outputs a frame, input to one of the ports, to another port corresponding to a destination. As a result, forwarding of the frame is performed between the multiple apparatuses.
There is also a bridge apparatus into which multiple line cards (e.g., interface cards or communication cards) can be incorporated. Each of the line cards has multiple physical ports coupled to the terminal apparatuses. A first one of the line cards transmits (or forwards) a frame, input to one of the physical ports, to a second one of the line cards which has the physical port corresponding to a destination address. The second line card outputs the transmitted frame to another physical port corresponding to the destination address. As a result, forwarding of the frame is performed between the multiple apparatuses.
Each line card manages a MAC (media access control) address table in which MAC addresses of the terminal apparatuses coupled to the physical ports of the line card and the physical ports of the other line cards are associated with the physical ports and the line cards. More specifically, each line card refers to, of a MAC destination address (MAC DA) and a MAC source address (MAC SA) which are included in the frame, the MAC source address to thereby learn the MAC address of the terminal apparatus as well as the physical port and the communication card to which the terminal apparatus is coupled. Thereafter, when a frame is input, the line card refers to the MAC address table to determine which line card and which physical port therein the input frame is to be output. The ingress line card (i.e., the line card to which the frame is input) then adds, for example, in-apparatus header information (or a routing header) to the frame and transmits the resulting frame to another line card in the bridge apparatus. On the other hand, when a frame including a MAC destination address that is not stored (i.e., not contained) in the MAC address table is input, the frame is broadcast to all of the physical ports of all of the line cards as a frame whose destination is unknown. This processing is referred to as “flooding”.
For example, Japanese Unexamined Patent Application Publication Nos. 2009-194706 and 2004-193821 are disclosed as related art.